The present disclosure relates to an apparatus and method for operating a resource in a wireless local area network (WLAN) system, and more particularly, to an apparatus and method for operating a resource in a WLAN system supporting a multi-user transmission scheme.
To meet the demand for wireless data traffic, which has increased since deployment of 4th-generation (4G) communication systems, efforts have been made to develop an improved 5th-generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post long-term evolution (LTE) System’.
It is considered that the 5G communication system will be implemented in millimeter wave (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To reduce propagation loss of radio waves and increase a transmission distance, a beam forming technique, a massive multiple-input multiple-output (MIMO) technique, a full dimensional multiple-input multiple-output (FD-MIMO) technique, an array antenna technique, an analog beam forming technique, and a large scale antenna technique are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, a device-to-device (D2D) communication, a wireless backhaul, a moving network, a cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation, and the like.
In the 5G system, a hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) modulation (FQAM), and a sliding window superposition coding (SWSC) as an advanced coding modulation (ACM) scheme, and a filter bank multi carrier (FBMC) scheme, a non-orthogonal multiple access (NOMA) scheme, and a sparse code multiple access (SCMA) scheme as an advanced access technology have been developed.
A communication system has evolved to support a high data rate in order to satisfy a demand for wireless data traffic which continuously increases. For example, a communication system has evolved to improve a spectral efficiency and increase a channel capacity based on various schemes such as an orthogonal frequency division multiplexing (OFDM) scheme, a MIMO scheme, and the like in order to increase a data rate.
For example, a WLAN system may use a multi-user multiple input multiple output (MU-MIMO) scheme that includes a plurality of stations (STAs) and a plurality of antennas, an orthogonal frequency division multiple access (OFDMA) scheme that uses a plurality of channels at the same time, and the like in order to support a mass data service.
Meanwhile, a medium access control (MAC) protocol, an institute of electrical and electronics engineers (IEEE) standard that operates based on a contention-based scheme, regards two signal transmissions which are simultaneously performed at a specific timing point as a collision. However, in a MIMO environment, where a plurality of antennas may be used, two or more than two signal transmissions may be detected at the same time. As such, a scheme in which a signal is transmitted to a plurality of STAs using a plurality of antennas, e.g., a MU-MIMO scheme, may be supported.
In a multi-channel environment which a plurality of channels are used at the same time, two or more signal transmissions may be detected through different channels. Thus, a scheme in which a signal is transmitted to a plurality of STAs using a plurality of channels, for example, an OFDMA scheme may be supported. Thus, an IEEE standardization for supporting a MU-MIMO scheme and an OFDMA scheme in a physical (PHY) layer and a MAC layer has been developed.
A structure of a conventional WLAN system supporting a multi-user transmission scheme will be described with reference to FIG. 1.
FIG. 1 schematically illustrates a structure of a conventional WLAN system supporting a multi-user transmission scheme.
Referring to FIG. 1, the WLAN system includes an access point (AP) 111, and a plurality of STAs, e.g., five STAs, i.e., STA#1 113, STA#2 115, STA#3 117, STA#4 119, and STA#5 121.
The STA#1 113, STA#2 115, STA#3 117, STA#4 119, and STA#5 121, and the AP 111 may monitor a channel to receive a related signal.
Upon detecting that a signal is to be transmitted, each of STA#1 113, STA#2 115, STA#3 117, STA#4 119, and STA#5 121, and the AP 111 transmits a related signal if a channel state indicates that a number of slots in an idle state is greater than or equal to a threshold slot count. In a WLAN system, an uplink and a downlink are implemented based on a contention-based scheme.
Thus, if a collision occurs in the uplink and/or the downlink, each of STA#1 113, STA#2 115, STA#3 117, STA#4 119, and STA#5 121, and the AP 111 performs a backoff operation that each of STA#1 113, STA#2 115, STA#3 117, STA#4 119, and STA#5 121, and the AP 111 waits until the channel state indicates that the number of slots in the idle state is greater than or equal to the threshold slot count to transmit a related signal again.
A structure of a conventional WLAN system supporting a multi-user transmission scheme has been described with reference to FIG. 1, and a resource operating process performed in a conventional WLAN system supporting a multi-user transmission scheme will be described with reference to FIG. 2.
FIG. 2 schematically illustrates a resource operating process in a conventional WLAN system supporting a multi-user transmission scheme.
Referring to FIG. 2, the conventional WLAN system is the same as the WLAN system in FIG. 1.
Firstly, an AP 111 transmits a beacon signal at operation 211, and each of STA#1 113, STA#2 115, STA#3 117, and STA#4 119 is allocated a resource from the AP 111 upon detecting a signal is to be transmitted. Each of STA#1 113, STA#2 115, STA#3 117, and STA#4 119 thus transmits a resource allocation request message to the AP 111. In FIG. 2, it will be assumed that STA#2 115 transmits a resource allocation request message to the AP 111 at operation 213, STA#1 113 transmits a resource allocation request message to the AP 111 at operation 215, STA#4 119 transmits a resource allocation request message to the AP 111 at operation 217, and STA#3 117 transmits a resource allocation request message to the AP 111 at operation 219. In FIG. 2, it will be noted that the resource allocation request message is illustrated as ‘Request’.
In the embodiment shown, the AP 111 uses a plurality of antennas, e.g., two antennas. As such, while the AP 111 may receive the resource allocation request messages from STA#1 113, STA#2 115, STA#3 117, and STA#4 119, the AP 111 may only allocate resources to two of the STAs, for example, STA#2 115 and STA#1 113, and transmit information, for example, scheduling information on the allocated resources at operation 221. After a short interframe space (SIFS), the AP 111 receives an uplink signal from each of STA#1 113 and STA#2 115 labeled as ‘UL MU-MIMO Data’ at operations 223 and 225, respectively.
Upon receiving the uplink signal from the each of STA#1 113 and STA#2 115, the AP 111 transmits an acknowledgement (ACK) signal to the uplink signal received from STA#1 113 and STA#2 115 at operations 227 and 229.
The ACK signal may be one of a block MAC protocol data unit (MPDU), an aggregated MPDU (A-MPDU) or a block MAC service data unit (MSDU), and a block ACK (BA) or BACK signal to an aggregated MSDU (A-MSDU).
As described above, in a WLAN system supporting a multi-user transmission scheme, an AP may allocate a resource to up the number of antennas used in the AP. However, the number of STAs to which the AP provides a service may be significantly greater than the number of antennas used in the AP. For example, if the STAs to which the AP provides the service transmit a resource allocation request message at the same time, a collision may occur. In this case, due to the collision, the STAs may transmit a resource allocation request message to the AP again after a preset backoff time has elapsed.
That is, if a resource allocating process is performed in the manner described above, a collision may occur. In this case, efficiency of a radio resource may be decreased and service delay may occur due to a transmission of a resource allocation request message in STAs.
As such, there may be a need for a resource operating method of preventing a collision and decreasing service delay in a WLAN system supporting a multi-user transmission scheme.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.